Radiant energy high-temperature heating apparatus



Feb. 27, 1951 w, PAR ER 2,543,053

RADIANT ENERGY HIGH-TEMPERATURE HEATING APPARATUS Filed Dec. 1, 1947 mam/6 fQlI/PME 7' py/v p D-C'. POWER (4452f INVENTOR. Q 100/5 W. PAR/(El? Patented Feb. 27, 1951 UNITED s TATE-s PATENT oaF-i CE 'RADI'ANT'ENERGY HIGHlTEMPERATURE HEATING APPARATUS Louis Parker, Little Nck, -N assignor to International :Standard :Electric *(io'rporation,

New York, -N. 3L, :"a corporation of :Delaware 'ApplicationDeceniber 1, 1947;"S'erialNo; 789,058

8 Claims. 1

'This invention relates 'to'radio-=freqiiencyheat generators, and more particularly to apparatus for concentrating radiant'energyina small space in orderto subject a mass-of material-to extremes of heat.

Briefly, the invention comprises a small-radioantenna mountedat one focus-of an-l1ipsoidal vessel, the object "to be heated being located at theother focus. The vessel is metallic, 'so as to produce reflections at high efiici'ency and to focus the reflected energy at the point of utilization.

It "is an object of m invention to *provide appar'atus for radiant energy heating which will be useful as a new-toolfor research.

Another object is to provide "a container "for ages to be heatedby radiant-energy andto-provide m'eans for holding the container in a solid state notwithstanding theeiitremely high temperatures to which the gas is heated.

Still another object is to provide means for dissipating radio-frequency energy through a gaseous medium inwhich a flow of free-electrons is produced byanexternally fed arc discharge. Other objects and advantagey'of "my invention may be inferred from the moredetailed-description to follow. This'descriptionis accompanied by a drawing'in which:

'Fig. 1 is a diagrammatic representation of radiant energy reflections withinan ellipsoidal container; and

Fig. 2 shows a preferred embodimentpf "a'p- 'paratus for carrying out the invention; the ellipsoidal container being sectioned andother-relat'ed apparatus units being indicated byblo'cks because of their well-known structure.

According to we'll-knowngebnietrical laws it will 'be understood thatany 'radiation originating at one focus of anellipsoid'will-be-:transferred to the other focusby reflection from thewalls.

In Figs. 1 and 2 the vessel 1 is shown to be ef ellipsoidal shape. An antenna which may be-of dipole type is located at onefo'cus-i while' the object to be h'eatedis lOcatedat thebther focus 3. A ray of energy such a's4 would-bereflected as a ray 5. Ray 5-if not completelyabsorbed by the object at focus 3 would bedire'cted along the line 6 and upon being-again reflected would follow the course 1 back to the focus .2. 1f this coursewere-extended still iurtheryanother. reflection would result in the residue of the energy being directed along the line 8 which is aimeduat the focus 3 wherean object is :to be heated. so, irrespective of the direction which any ray-of energy takes upon leaving the antenna, it will always be reflected by the inner surface'of the ellipsoidtoward the other -focus' 3' where the objectis'positioned. A

By making "the sum of the distances of the rays-'-4and5fequal to'awhole number of multiples of half wavelength, standing waves may be set up. .At each're'fiection, therefore, the Waves are combined"additivel'yin" phase instead of'at ran- 'dom pliaseas'wo'uld otherwisebe the case.

The antenna at focus Zmay befed'withmicrowaveenergy as'generate'd by anoscillator' 9. 'The energy iscondu'cted into the vessel I by means of .a transmissionline I0. .Suitable well known means may be provided for cooling the transmis- .sion line. Thisis conventionallyindicated by the rectangle -l l,-glab'eled Cooling Equipment, and pipes 12 may be used to carry a 'cooling fluid to and fromthe transmission line.

According-to one lTiOdEOf operation the substanceto be'heat-treated maybe in .a'semi-liquid, or-plastic state and may be:pumped into the vessel through :a .pipe :13 *whichl-l'ea'ds to the focus :3. 'I heipump 14- is shown diagrammatically.

In 'orderto provide an ionized gas in which to immerse the substance to be heated, and also for supplementing the "radio-frequency heating source by other heating means, I may mount two carbon' rods- I5 across which an arc plasma disicharge or. positive' columnamay be maintained'at .the-fo'ousii. Becauseof the section plane of Fig. z only one of the :rods [5:IisTsh0Wn. The resulting arc, the niiddle of which is coincident'with the working f0cus,"'serves to vaporize and ioniz the=materialto beheated. The radio frequency power .at'tliis focus isusedto further raise-the temperatureof the ionized gases in the arc. 'The rods may be "held in sock'et's '16 and may be fed with direct current through cables I 1 connected to any'suitable-sour'ce. The vessel may be jacketed with any suitable layer of heat-"insulating material [8.

Under certain-circumstances -it-may be important to treat the substance in 'anatmosphere 'of compressed gas. "Withthis purpose in view "a compressor 1'9 is'fprovided. Its output is piped into thevessel in 'anysuitable' manner. Awindow 2'0 'isprovid'ed for viewing the operations inside the'vessel. The window may be composed'of quartz, if desired, in "order to withstand the heat. It is securely set in place,"iorming ahermeti'c seal. The vessel maybe made in two pieces and boltedtogether at their abutting flanges '2l by means of bolts 12. Thislarrangement, of course, facilitates replacement of the carbon electrodes for the arc discharge and of the material to be treated, or the removal of the same after treatment.

That it is possible to generate heat and to concentrate the same in a small zone at extremely high temperatures by the use of my invention may be better understood from the following brief discussion of the theory of operation.

Heating of the gases resulting for the vaporization and ionization of the material disposed at the center of the arc, which are ionized in the plazma, or positive column, of an arc discharge results from the absorption of electromagnetic waves, particularly of very high frequency.

The energy of the waves so absorbed is changed to heat and light. While waves of any length are absorbed to a degree by the gases, there is a great difference in the absorption coefficient of any gas for various wavelengths. This is the well known phenomenon of selective absorption, where a number of narrow bands of frequencies find the gas almost entirely black. Different elements are selective for different frequencies. Much of the wavelength region the invention contemplates using is unexplored, but in the opinion of experts a very pronounced selective absorption will take place in this range except that as the wavelength increases, the absorption coeflicient drops. There are known mathematical formulas with which these various wavelength ranges can be determined, making it possible to design the oscillator for the wave length necessary to heat any desired element.

One example of the absorption of short radio waves by ionized gases can be found in the June 1934 issue of the IRE proceedings, under the title Ionized gas modulators by Linder and Wolff. These writers describe a way of absorbing cm. waves by a gas in varying amounts by varying the degree of-ionization. Their measurements showed that most of the energy in a concentrated beam of 10 centimeter waves is absorbed when passing thru a thickness of cm. of ionized gas. The above mentioned selective absorption was not made use of in this experiment. It was found that the amount of energy reflected and refracted was small in comparison to the absorbed part.

One phenomenon that will be noticed when the apparatus shown in Fig. 2 functions is the strong convection currents set up by the difference of temperature in different parts of the gas. Too strong convection may blow out the arc. Also it may not permit the gas to remain long enough in the working focus to reach the highest temperature the apparatus is capable of imparting to it. These effects are reduced by using R. F. pulses instead of a sine wave, since convection currents are caused by the average rather than instantaneous heat. It was found by calculation that 160 kilowatts of pulses can raise the temperature of the gas in the working focus from 3000 Kelvin to 6000" Kelvin in less than l/lOO second. This sudden temperaturechange is possible due to the low specific heat of the highly expanded gases. Most of'the energy supplied takes care of the 'heat radiation which is extremely high at 6000 Kelvin. Much of the heat radiated, however, is returned to the working focus after two or more reflections. This gives the apparatus high thermal efficiency. The electrical efficiency is also good due to the reflections. The effect of the reflections on the dipole is to decrease its resistance. It is not a serious problem, however, to match this lowered radiation resistance.

The dipole at the focus 2 is subject to a concentration of heat and radio waves almost as much as the material in the working focus 3. It is important, therefore, that the dipole be composed of a metal capable of withstanding high temperatures and that it be polished. The pipes I2 for the cooling fluid may be connected to hollow conductors constituting the transmission line In in order that the cooling fluid may reach the dipole. Live steam may be used for absorbing the heat, or other fluids may be used optionally.

In addition to high temperatures the apparatus shown in Fig. 2 is also capable of generating treme intensities of light. The temperature of the gases is about the same as on the surface of the sun, giving the greatest intensity in green.

In a practical embodiment of my invention the vessel I may be built to have a ten-foot length along its major axis. The average radio-frequency power input may be of the order of 1.6 kw. at approximately 3,000 mc., while the direct current for the arc may be about 10 kw. Almost all of this energy must be dissipated through the wall of the vessel i, and in so doing its temperature may be raised to just below red heat.

The ellipsoid vessel 1 may be made of cast steel with heavy copper plating inside, polished to a mirror finish. If the copper tends to react with the various chemicals within the ellipsoid, it can be replaced by some noble metal like platinum or lrridium. A quartz lining inside this vessel is also feasible.

As an example of what practical results could be accomplished with this invention, the extraction of aluminum from clay may be cited. There is a great abundance of aluminum on earth, but so far its removal was only possible from bauxite, a mineral found only in a few parts of the globe.

Among the many uses to which my invention may be put, its use for the extraction of metals affords a sufhcient illustration of how it may be made to operate. Assume, for example, that metals such as aluminum, sodium, potassium and magnesium are to be separated from clay. The process suggested is as follows:

The clay in the soft solid state is pumped by pump 14 thru pipe [3 into the ellipsoid, where it is first vaporized, then heated periodically to the temperature where chemical compounds can no longer exist. This happens at about 6,000 centigrade. The mechanical mixture of the various elements moved by convection currents cools off slightly after each heating period and the aluminum recombines with another element, such as oxygen. After this, the aluminum oxide condenses and solidifies on the bottom of the vessel, from where it is removed periodically. The bottom of the vessel may contain a dish of the proper shape adhering to the contour of the vessel, where this solidification takes place. It is this dish which is removed periodically. The aluminum oxide is then reduced by conventional means to pure aluminum.

Sodium, potassium and magnesium may also be freed from their compounds by heat as above and oxidized or otherwise recombined before cooling off completely.

The highest temperature available to the research chemist until the present, was the electric are. With the use of this invention additional energy in the order of kilowatts or more is supplied to a substance which has reached about the highest temperature the ionized gas in the arc is capable of imparting to it.

The problem of a container capable of holding material at a temperature so high that matter can exist only in a gaseous state is solved with this invention. Convection currents are used to carry matter in and out of the high temperature zone. 'In this Way chemical compounds are first disintegrated and later new compounds formed.

While it is believed that my invention may be used for exploring many diiferent physical phenomena, the basic principles are well illustrated in the example given above. The scope of the invention is not, therefore, restricted to what has been shown and described.

I claim:

1. A device for obtaining a high temperature in a limited space, comprising an ellipsoidal shell having an electro-magnetic radiant energy reflecting inside surface, an antenna centered at one focus of said shell, means for producing an arc discharge at the other focus of said shell, a substance to be heated situated in the path of said are discharge for vaporization and ionization thereby and high frequency energy fed to said antenna, whereby radiant energy by radiation and reflection from the inner wall of said shell is directed to a point within said are and is absorbed by the ionized vapors of said substance to produce a high temperature.

2. A device according to claim 1 in which the frequency of said energy is suitably chosen with respect to the distance of travel of the energy from said antenna to the inner wall of the shell and thence to the point of location of said are so that the reflected rays of said energy will be cophasally concentrated on said substance.

3. Apparatus for the treatment of substances with extremely high temperatures, comprising a metallic ellipsoidal shell, having an electromagnetic radiant reflecting inside surface, means for supporting a substance to be treated in a zone at the center of which is one focus of said shell, means for vaporizing the substance to be treated into an ionized gaseous medium in that zone, and means for radiating electromagnetic energy in all directions from the other focus of said shell, which energy upon reflection from the inner wall of the shell is focussed on said substance and absorbed by the ionized vapor thereof.

4. Apparatus according to claim 3 wherein said means for vaporizing the substance into an ionized gas includes a power supply connected to electrodes across which an arc discharge is produced.

5. Apparatus according to claim 3 and including a window in said shell, said window being glazed with a transparent heat resistant material, such as quartz, whereby said substance may be observed while being subjected to heat treatment.

6. Apparatus according to claim 3 wherein said shell is composed of two flanged parts the flanges of which are bolted together during a process of heat treatment, the parts being separable for obtaining access to said substance.

7. Apparatus according to claim 3 wherein the inner wall of said shell is lined with quartz.

8. Apparatus according to claim 3 further including a gas compressor to maintain the inside of said shell at a given higher than normal pressure.

LOUIS W. PARKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 886,856 Price May 5, 1908 2,245,669 Hollmann June 17, 1941 2,364,526 I-Iansell Dec. 5, 1944 OTHER REFERENCES Hershberger et al., Thermal and Acoustic Effects Attending Absorption of l\ficrowaves by Gases, RCA Review, September 1946, vol. VII, No. 13, pages 422-431, particularly pages 422, 423 and 428.

Engineering Abstracts, Product Engineering, January 1947, pages 137-140, particularly page 138. 

